An aircraft having an engine supported in the airframe mounted configuration comprises an engine and a nacelle structure housing said engine. The nacelle structure comprises two displaceable parts called fan cowl doors or cowlings which can be opened on the ground during maintenance operations to access the various items of the engine. The cowlings or fan cowl doors are closed and properly latched during operational conditions of the aircraft, providing aerodynamic continuity for the engine during flight. The cowls doors are typically hinged to the top of the nacelle so that they can rotate upwardly or downwardly relative to the nacelle and are arranged symmetrically on different sides of a mast or a pylon on which the nacelle is suspended to a wing of the aircraft.
The nacelle usually also comprises fan cowl doors latching systems fixing and latching the fan cowl doors during operation of the aircraft.
These latching systems are used to secure the two cowl doors together in the closed position. Typically, the two cowl doors are held together with a plurality of latching systems. Each latching system usually has an anchor (also sometimes referred to as a keeper) provided at a lower edge of a first cowl door, and a latch provided at a lower edge of a second cowl door. The latch has, among other portions, a hinged hook for coupling to the anchor, and a handle. Such a latch is known from, for example, U.S. Pat. No. 4,531,769.
The latching system is able to occupy two states. In a first state the hook is coupled to the anchor and the latching system maintains the cowl doors in a closed position. If the handle is in a closed position, the latching system is supposed to be closed and the cowl doors are supposed to be secured and closed.
The second state of the latching system is one in which the hook is uncoupled from the anchor and thus, the cowl doors are not secured to each other or maintained in a closed position. Typically, in this state the handle is in the open position and hangs down underneath the cowl doors providing a visual indication that the cowl doors are not secured and/or in the closed position.
However in conventional latching systems, it is possible for the handle to move to the closed position even if the cowl doors are not secured to each other. Thus, while the handle may be in the closed position, the cowl doors may not be secured together in the closed position. Therefore, the handle cannot effectively function as a visual indicator that the cowl doors are not secured together.
Indeed, it is important to verify that the latching systems are each secured and locked before the take-off of the aircraft. If the cowl doors are in the closed position, but not secured together (i.e., having unsecured latching systems), they can be ejected from the aircraft due to the air pressure during the flight.
Furthermore, under its own weight, and because of the position of its pivot axis, a cowl door tends to rotate downward to a resting position similar to its closed position. This may make it difficult for an operator to visually determine if the cowl doors are actually secured together and fully closed by the latching system, or merely “resting.”
Moreover, there is a current trend towards the utilization of aircraft engines that include a high bypass ratio and have a fan diameter between 3-4 meters. The use of such large engines decreases the ground clearance of the nacelle. Accordingly, it can be very difficult for an operator to visually verify if the cowl doors are secured and closed by inspecting the handles of the latching systems.
Therefore, there is a need for a latching system that addresses these concerns.